Lost circulation is a problem in the oilfield industry. Many technologies have been used to help combat lost circulation. Polymer pills, reactive mud chemistries, fibers, flakes, sized granules based on optimum particle size distribution or ideal packing theory, resilient materials, water swellable polymers, thixotropic cements are some of the methods used to attempt combat lost circulation.
Thixotropic agents can provide fluids with the ability to lose viscosity when being sheared, such as by pumping, and then to return to a highly viscous form when at rest. The use of thixotropic agents for treating drilling fluids and well-servicing fluids is known. For example U.S. Pat. No. 4,888,120 describes adding synthetic layered silicates combined with synthetic polymers to make a high temperature stable thixotropic material to be added to the water based drilling fluids during preparation of the fluid.
WO9620899 describes a thixotropic material comprising smectite clays which is capable of rapid gelling for cementicious formulations to help plug lost circulation zones.
U.S. Pat. No. 4,663,663 discloses a shear thickening composition for well control fluids comprising a water-in oil emulsion having clay dispersed in the oil phase and the aqueous phase containing dissolved polyacrylamide and a polycarboxylic acid. Each of the dispersed aqueous droplets being coated with a polymeric material that is broken when subjected to high shear forces.
The present invention provides a method to impart thixotropy to fluids downhole at a known location so as to prevent loss circulation and improve wellbore strengthening during drilling, and/or assist cuttings removal from the wellbore.